Oligomers of fluorinated olefins

ABSTRACT

Oligomers of compounds of the formula 
     
         X--(CF.sub.2).sub.a --O.sub.b --(CH.sub.2).sub.c --CH=CH.sub.2( 1) 
    
     and co-oligomers of compounds of the formula (1) together with compounds of the formula 
     
         X--(CX.sub.2).sub.d --O.sub.b --(CX.sub.2).sub.c --CX=CX.sub.2( 2) 
    
     in which X is hydrogen or fluorine, a is a number from 2 to 16, b and c are, independently of one another, 0 or 1, and d is a number from 0 to 6, with a mean degree of oligomerization of 2 to 4, are obtained by heating a solution of the monomers in a hydrocarbon together with a free radical-forming catalyst to 135° to 180° C. The oligomers are lubricating agents and lubricants.

DESCRIPTION

The invention relates to oligomers of compounds of the formula

    X--(CF.sub.2).sub.a --O.sub.b --(CH.sub.2).sub.c --CH=CH.sub.2( 1)

and co-oligomers of compounds of the formula (1) with compounds of theformula

    X--(CX.sub.2).sub.d --O.sub.b --(CX.sub.2).sub.c --CX=CX.sub.2( 2)

In these formulae: X is hydrogen or fluorine, a is a number from 2 to16, b and c are, independently of one another, 0 or 1, and d is a numberfrom 0 to 6.

Oligomers in which X is fluorine, a is a number from 4 to 12, and b andc are both zero are preferred.

The mean degree of oligomerization of these compounds is 2 to 4.

The oligomers according to the invention are obtained by heating asolution of at least one compound of the formula (1), optionally with atleast one compound of the formula (2), in a hydrocarbon to a temperatureof 135 to 180° C. together with a free radical-forming catalyst.

Preferred solvents are saturated hydrocarbons such as alkanes with 5 to12 carbon atoms and readily accessible cycloalkanes such as cyclohexane.

Preferred free radical-forming catalysts are peroxides, especiallydialkyl peroxides. Symmetrical dialkyl peroxides having in each alkyl 6to 16 carbon atoms are particularly preferred.

The preferred reaction temperature is in the range from 140° to 160° C.

Preferred starting materials of the formula (1) areperfluoroalkylethylenes having a perfluoroalkyl radical with 4 to 12carbon atoms, and the corresponding compounds with a terminal hydrogenatom on the fluoroalkane chain. Furthermore, the corresponding vinyl andallyl ethers are preferred.

Preferred comonomers of the formula (2) are optionally fluorinatedmono-ethylenically unsaturated hydrocarbons with 2 to 6 carbon atoms aswell as optionally fluorinated alkyl vinyl and alkyl allyl ethers.Ethylene, 1-octene, 1,1,2,2-tetrafluoroethyl 3',3'-difluoroallyl etheras well as hexafluoropropene may be mentioned.

The oligomers and co-oligomers according to the invention are highlyhydrophobic and relatively oleophobic, but are fluorophilic, and aretherefore suitable for use as lubricants on surfaces, particularly ofplastics, metal or glass. The products can for example easily be appliedby simply rubbing them on polyethylene sheets. Upon the slightestshaking water runs in the form of almost spherical droplets over thesurface of sheets treated in this way, whereas water clearly adheres tountreated sheets. If the compounds according to the invention areapplied to the undersides of polyethylene skis optionally treated withgraphite, this produces a very good running behavior on wet snow. Thecompounds may be applied in a conventional manner, for example as skiwax. The compounds according to the invention can also be processed, bythe pressure sintering technique, together with polyethylene to form amaterial from which ski coatings with a high degree of slip can beprepared.

Since the oligomers according to the invention are miscible withperfluoroalkanes, fluoroalkane waxes that are otherwise difficult toapply to surfaces can be applied with their help.

Extremely thin oligomer films greatly reduce glass-on-glass friction.Metal-metal friction too is greatly reduced. An addition ofpolytetrafluoroethylene micropowder produces a further improvement.

The compounds according to the invention are thus outstandingly suitablefor coatings of a very wide range of surfaces, the friction beinggreatly reduced on surfaces coated in this way.

The invention is described in more detail in the following examples. Themolecular weights were determined with a vapor pressure osmometersupplied by Knauer.

EXAMPLE 1

An electrically heated rocking autoclave of 4.5 1 capacity is chargedwith a solution of 1730 g (5.0 mol) of C₆ F₁₃ CH=CH₂ and 51.2 g (0.35mol) of di-tert-butyl peroxide in 2.0 1 of n-hexane. The autoclave isflushed for 10 minutes with a gentle stream of N₂, the nitrogen pressurein the autoclave is then raised to 10 bar N₂ for a pressure test, andthe pressure is slowly released. The autoclave is then heated to 150° C.over 1.5 hours while shaking, and is shaken for 5 hours at thistemperature. After cooling to 30° C. (external cooling by blowing withcold air) the autoclave is emptied. A 2-phase mixture is obtained, theupper phase composed mainly of hexane. The solvent is removed in arotary evaporator. The remaining crude product is suction-filtered undera slight vacuum using a paper filter, in order to remove minormechanical impurities. The filtrate is distilled with a Vigreux column.A total of 133 g of product distill off at a head temperature of between25° and 105° C. under 20 mbar. The average molecular weight M is 562,i.e. the distillate contains about 60% of dimers. 1593 g of an almostcolorless oil are obtained as residue (92.1% yield). The average molarmass is 1070, which is slightly above the molar mass of the C₆ F₁₃CH=CH₂ -trimer (1038).

The oligomeric product is extremely resistant to hot sodium hydroxide.After stirring for 3 hours under reflux with 20% strength NaOH (with andwithout phase-transfer catalyst), only traces of fluoride were found inthe aqueous phase.

EXAMPLE 2

The same procedure as in Example 1 is adopted, except that cyclohexaneis used as solvent. A comparable product is obtained in 91% yield.

EXAMPLES 3 TO 10

The preparation of further oligomers is described in the following Table1, and the production of co-oligomers is described in Table 2.

Examples 7 to 10 were carried out using in each case 100 ml of hexane assolvent.

                                      TABLE 1                                     __________________________________________________________________________    Alkene                  DTBO.sup.a)                                                                           n-Hexane                                                                            Temperature                                                                          Duration                                                                           Yield                                                                              Features of            Example                                                                             type      g   mol g   mol %                                                                             ml    °C.                                                                           h    g    the                    __________________________________________________________________________                                                           product                3     C.sub.8 F.sub.17 CH═CH.sub.2                                                        133.8                                                                             0.3 3.07                                                                              7   120   150    5    108.0                                                                              thick oil              4     R.sub.F CH═CH.sub.2.sup.b)                                                          119.9                                                                             0.25                                                                              2.56                                                                              7   100   150    5    115.3                                                                              partially                                                                     solid.sup.c)           5     R.sub.F CH═CH.sub.2.sup.b)                                                          1438.5                                                                            3.0 30.7                                                                              7   1200  150    5    1325 partially                                                                     solid.sup.c)           6     C.sub.8 F.sub.17 CH.sub.2 CH═CH.sub.2                                               115 0.25                                                                              2.56                                                                              7   100   150    5    113.0                                                                              yellowish              __________________________________________________________________________                                                           oil                     .sup.a) Di-tert-butyl peroxide                                                .sup.b) Technical product: R.sub.F = 4.3% of C.sub.6 F.sub.13, 44.0% of       C.sub.8 F.sub.17, 39.1% of C.sub.10 F.sub.21, 3.4% of C.sub.12 F.sub.25       and longerchain compounds, remainder impurities such as R.sub.F H.            .sup. c) Homogeneous liquid above 40° C. DSC measurements under        autogenous pressure did not show any significant decomposition up to          400° C.                                                           

                                      TABLE 2                                     __________________________________________________________________________    Alkene I             Alkene II           DTBO.sup.a)                                                                         Temperature                                                                          Duration                                                                           Yield              Example                                                                             Type    g  mol Type         g  mol g     °C.                                                                           h    g                  __________________________________________________________________________    7     C.sub.6 F.sub.13 CH═CH.sub.2                                                      69.2                                                                             0.2 C.sub.6 H.sub.13 CH═CH.sub.2                                                           22.4                                                                             0.2 2.34  150    5    82.9               8     C.sub.6 F.sub.13 CH═CH.sub.2                                                      86.5                                                                             0.25                                                                              CH.sub.2 ═CH.sub.2                                                                     14 0.5 2.56  150    5    97.9               9     C.sub.6 F.sub.13 CH═CH.sub.2                                                      51.9                                                                             0.15                                                                              CH.sub.2 ═CHCH.sub.2 OCF.sub.2 CF.sub.2 H                                              15.8                                                                             0.1 2.56  150    5    68.0               10    C.sub.6 F.sub.13 CH═CH.sub.2                                                      86.5                                                                             0.25                                                                              CF.sub.2 ═CF--CF.sub.3                                                                 37.5                                                                              0.25                                                                             2.56  150    5     .sup.                                                                        80.6.sup.b)        __________________________________________________________________________     .sup.a) Di-tert-butyl peroxide                                                .sup.b) Hexafluoropropene proportion: 27.0 mol %                         

EXAMPLE 11

A mixture of 3.2 1 of a higher alkane mixture (SHELLSOL 145/160) ofboiling point range 145° to 160° C., 4088 g (about 8 mol) ofperfluoroalkylethylene and, dissolved in the latter, 82 g (0.56 mol) ofdi-tert-butyl peroxide is aspirated into an evacuated 10 1 capacitystirred autoclave. The perfluoroalkylethylene had the followingcomposition (as determined by gas chromatography):

    ______________________________________                                        C.sub.n F.sub.2n+1 --CH═CH.sub.2                                                                       98%                                              n =  8             1.2%                                                       n = 10            67.5%                                                       n = 12            24.8%                                                       n = 14             4.1%                                                       n ≧ 16      0.4%                                                       C.sub.n F.sub.2n+1 --H:      0.3%                                             other impurities             1.7%                                             Iodine content:              390 ppm                                          ______________________________________                                    

The residual vacuum is filled with nitrogen and the autoclave is flushedwith nitrogen at a pressure of 5 bar. The pressure in the autoclave isreleased, the autoclave is closed and then heated to 150° C. within 1.5hours and the contents are stirred for 5 hours, a maximum pressure of 6bar being measured. The autoclave is then allowed to cool to about 80°C. and is emptied through a dip tube. The liquid, two-phase reactionproduct is distilled up to a bottom temperature of 150° C. under 20mbar. The solvent that passes over contains only very small amounts offluorinated components and can be used without further purification foranother run. The liquid distillation residue (4170 g) solidifies to aneasily grindable product, which is still free-flowing after prolongedstorage. The melting range is 70° to 80° C.

If a perfluoroalkylethylene containing lower boiling fractions is used,solidifying products with a lower melting range are obtained; forexample, when using C_(n) F_(2n+1) --CH=CH₂

    ______________________________________                                        n =  6      30.3%      n = 12     16.4%                                       n =  8       4.1%      n = 14      4.7%                                       n = 10      39.9%      n ≧ 16                                                                             1.6%                                       iodine content: 200 ppm                                                       ______________________________________                                    

a product is obtained having a melting range of 40° to 60° C.

EXAMPLE 12

The oligomer according to Example 5 is applied by spincasting from a1,1,2-trifluorotrichloroethane (.sup.• Frigen 113) solution to acarefully cleaned glass plate. After evaporating off the solvent theplate is heated to 40° C. in order to orient the surface film. Adispersive surface energy of only 9 mN/m is calculated from the contactangles θ measured by immersion with n-dodecane and n-hexadecane(according to W. A. Zisman "Contact angle, wettability, and adhesion",Adv. in Chemistry Series, No. 43, Am. Chem. Soc., Washington DC, 1964).

EXAMPLE 13

5000 g of high molecular weight, microgranular polyethylene (.sup.•Hostalen GM 7250, Hoechst AG), 1250 g of amorphous carbon (acetylenesoot) and 100 g of the perfluoroalkylethylene oligomer according toExample 5 are premixed in batches. The mixture is homogenized in aplanetary mixer at a maximum temperature of 70° C. and is thenisostatically compressed and sintered into a cylinder in a heated moldwhile gradually raising the temperature to 200° C. and under a maximumpressure of 200 bar. After cooling, a 1.5 mm thick, almost black slicedsheet is produced from the molding obtained as described above. Thissheet is polished to produce a smooth, crack-free surface, as isrequired for a top-quality coating for racing skis.

Compared to a sliced sheet produced in the same way but without additionof the oligomer, the sheet according to the invention is considerablymore water-repellent. Investigations by scanning electron microscopy andESCA (electron spectroscopy for chemical analysis) show that theoligomer accumulates in particular in the surface regions composed ofamorphous polyethylene.

EXAMPLE 14

0.5 % by weight of the oligomer according to the invention is mixed withhigh molecular weight polyethylene (Hostalen GM 5010 T2) and extruded inan extruder to give tubes having a diameter of 32 mm and a wallthickness of 3 mm. With a screw speed of 80 r.p.m. and a melttemperature in the center of 223±1° C. and an external melt temperatureof 211±2° C., the melt pressure was 120 bar.

With a control batch without addition of oligomer, a melt pressure of135 bar was produced.

Compared to the tube obtained without addition of oligomer, the tubesextruded with addition of oligomer had a much higher gloss, and aviscous oil when flowing through the tube adhered very much lessstrongly to the tube wall.

The following oligomers were used:

Experiment 1: Product according to Example 5

Experiment 2: Product according to Example 11, melting range 40° to 60°C.

Experiment 3: Product according to Example 11, melting range 70° to 90°C.

I claim:
 1. An oligomer of compounds of the formula

    X--(CF.sub.2).sub.a --O.sub.b --(CH.sub.2).sub.c --CH=CH.sub.2( 1)

and co-oligomers of compounds of the formula (1) together with compoundsof the formula

    X--(CX.sub.2).sub.d --O.sub.b --(CX.sub.2).sub.c --CX=CX.sub.2( 2)

in which X is hydrogen or fluorine, a is a number from 2 to 16, b and care, independently of one another, 0 or 1, and d is a number from 0 to6, with a mean degree of oligomerization of 2 to
 4. 2. An oligomer ofcompounds of the formula (1) as claimed in claim 1, in which X isfluorine, a is a number from 4 to 12, and b and c are zero.
 3. A processfor preparing an oligomer or co-oligomer with a mean degree ofoligomerization of 2 to 4, which comprises:heating a solution of atleast one compound of the formula (1)

    X--(CF.sub.2).sub.a --O.sub.b --(CH.sub.2).sub.c --CH=CH.sub.2( 1),

or a mixture thereof with at least one compound of the formula (2)X-(CX₂)_(d) --O_(b) --(CX₂)_(c) --CX=CX₂ in which X is hydrogen orfluorine, a is a number from 2 to 16, b and c are, independently of oneanother, 0 or 1, and d is a number from 0 to 6,in a hydrocarbon to atemperature of 135° to 180° C. together with a free radical-formingcatalyst, and recovering a said oligomer or co-oligomer having a meandegree of oligomerization of 2 to
 4. 4. A grease or lubricantcomposition, comprising a hydrophobic grease or lubricant and anoligomer or co-oligomer as claimed in claim
 1. 5. A lubricantcomposition for the underside of skis, comprising a ski wax and anoligomer or cooligomer as claimed in claim
 1. 6. A wax compositioncomprising a fluoroalkane wax and an oligomer or co-oligomer as claimedin claim
 1. 7. A ski coating, consisting essentially of polyethylene andan oligomer or co-oligomer as claimed in claim
 1. 8. A plastic, metal,or glass substrate coated with an oligomer or co-oligomer as claimed inclaim
 1. 9. A plastic ski coated on its underside with an oligomer orco-oligomer as claimed in claim
 1. 10. A plastic ski as claimed in claim9, wherein the ski comprises polyethylene plastic.
 11. A metal or glassdevice comprising metal or glass parts, wherein the metal-metal frictionor the glass-glass friction is reduced with a film on metal or glasssurfaces, said film comprising an oligomer or co-oligomer as claimed inclaim
 1. 12. A metal or glass device as claimed in claim 11, wherein thefilm comprises polytetrafluoroethylene micropowder in addition to saidoligomer or co-oligomer.
 13. A method of lubricating an article,comprising: applying to the surface of the article or including in thecomposition from which the article is made an oligomer or co-oligomer ofclaim
 1. 14. A method as claimed in claim 13, wherein said articlecomprises glass, metal, or plastic.
 15. A method as claimed in claim 14,wherein said plastic is polyethylene.
 16. A method as claimed in claim13, wherein the article is a ski, and the surface of the article is theunderside of the ski.